Die and the art of forming anchorage instruments



y 1939- H. ROSENBERG DIE AND THE ART OF FORMING ANCHORAGE INSTRUMENTS Filed Oct. 25. 1934 Patented July 4, 1939 DIE AND THE ART OF FORMING ANCHORAGE INSTRUMENTS Heyman Rosenberg, New York, N. Y.

Application October 23, 1934, Serial No. 749,643

Claim.

, 1,809,758, dated June 9, 1931, and N0. 1,827,615,

dated October 13, 1931, having more particularly in mind the provision of a longitudinal cut or groove, or a series of them, in' the finished fastener.

Though I have been manufacturing and marketing the several types of fasteners of said patents for many years in vast quantities running up into millions daily, and other manufacturers have for the past several years been putting out large quantities of the type of screw shown in my first above-mentioned patent, none of the fasteners manufactured by me has included the longitudinal cuts or grooves intersecting the threads as seen in the first above-mentioned patent, and most of those manufactured by others have not included, such groove. This omission has been in' part and probably largely due to the expense of producing the longitudinal groove or grooves. Heretofore, the groove or grooves along the screw body has or have been formed either before or after the thread is rolled thereon, usually afterward; and it has been customary to form the groove in each case by a separate cutting or abrading operation, either by sawing, grinding, milling, filing, or other cutting.

One,irnportant object of the present invention is the substantial saving of expense in producing instruments of this type provided with a groove or grooves intersecting thread helices.

It is another essential object of the present invention to provide such groove or grooves without the necessity for a separate operation or any cutting operation applied to the blank.

To this end, the invention includes the art of rolling a threaded fastener instrument for forming threads thereon and simultaneously rolling a groove or grooves therein intersecting the threads being rolled.

The invention also includes a novel die for thread rolling having projections on its face coordinated with each other and with the thread rolling ribs of the die for causingthe die to produce both a thread and a groove in a screw blank when the blank is subjected to the customary rolling action; and also includes a co-ordinated die cooperating with the thread-forming portion of the first-mentioned die and also acting onthat part of the blank being rolled with a groove for forming a thread along the blank intersected .by the groove.

The present invention is applicable regardless of a wide range of variation'of the contour of the thread and of the pitch of the thread. In commercial usage, threads 'of Screw-threaded fasteners are sometimes referred to as of machine screw pitch and sometimes as wood screw pitch with the usual distinction that the wood screw pitch is frequently higher than the standard machine screw pitch, but there are, of course, numerous instances of higher pitch for machine screws than for wood screws, so that the distinction between a machine screw thread and a wood screw thread in the final analysis is the use to which the threaded fastener is going to be put. The commonly used blunt or rounded entering end of a machine screw does not even distinguish since many wood screws are also made with blunt entering ends. Hence, reference to a wood screw usually indicates that the screw is intended for use in wood and is designed to form its own path in the work material into. which it is to be forced; whereas a machine screw presupposes that a tapped internal thread or previously prepared thread path is to be provided into which the machine screw is to be threaded. Accordingly, it should be understood that the present invention relates to the art and apparatus for rolling threaded fasteners and like instruments to form the threads and also to form the groove or grooves across the threads without reference to whether the pitch is high or low or commonly referred to'as machine screw threads or wood screw threads; but since the product in the form of a threaded fastener isqintended to find its own way into the material entered without having a previously formed thread path, the said product may be said to more nearly approach the wood screw concept of fastener regardless of whether the pitch be high or low than it does the machine screw idea.

In the accompanying drawing- Figure 1 is a top plan view of an ordinary thread-rolling die of the type usually employed as the stationary die in an automatic screw thread rolling machine. v

Figure 2 is an edge view thereof shown in its operative relation and new combination as when located in an automatic thread-rolling machine, the balance of the figure showing the present improved thread and groove rolling die in its proper relation as if located in an automatic thread-rolling machine and cooperating with the first die, a partially rolled blank being seen, and the parts being in the position of an inverted plan of the assemblage in such thread-rolling machine, the combined thread rolling and groove forming die being indicated as the moving die of such machine.

Figure 3 is a view similar to Figure 1 but showing the improved thread rolling and groove forming die.

Figures 4 and 5 are transverse sections taken n the planes indicated respectively by the lines 4-4 and 5-5 of Figure 3, parts being broken away in Figure 4 for the saving of space.

Figure 6 is a view in side elevation of a blank well adapted for being rolled by the combination of dies seen in Figure 2, the blank being shown on a somewhat enlarged scale over the scale of the showing of the dies.

Figure '7 is a similar view of the completed screw or fastener instrument.

Figure 8 is an end view thereof looking at the entering end.

Figure 9 is a view similar to Figure 8 of a slightly modified embodiment of screw.

I The well known popularity of rolled thread screws on the market is laregly due to their inexpensiveness of production and sufiiciently near approach to precision. Automatic machines are commonly employed for rolling such screws, and one form of such machines is shown in my copending application Serial No. 651,783, filed January 14, 1933, which machine includes a support for a fixed die and a reciprocating slide for a moving die for moving the reciprocating die lengthwise of and across the fixed die with the adjacent faces of the dies spaced to properly accommodate the blank therebetween that is being rolled. If the blank is perfectly cylindrical and the dies are flat, the conventional rolled thread screw results, but if the blank has a tapering entering end portion and the dies are flat and properly spaced to give the conventional thread on the major part of the blank, the tapered portion of the blank will have its thread of reduced outstanding depth tapering to the entering terminus blended in the body of the blank, and the resulting entering portion of the thread will be substantially that shown in my Patent No. 1,809,- 758, except for possible variations in thread pitch, width, cross section, and spacing, according to the particular dies employed, and also except for the fact that the thread shown in said patent is indicated as having been cut rather than rolled, since the entering terminus shows the groove in the median line of the thread terminating within the body of the original blank, a condition that would not ordinarily occur from a rolling operation. By increasing the pitch of the taper and providing an outstanding slant or diagonal portion along the edge of the die that forms the entering end portion of the thread, the structure of the screw seen in my Patent No. 1,827,615 may be produced by rolling. Should the blank have its tapering entering end extended to a complete cone and the outwardly turned or inclined portion of the die sufficiently extended and properly pitched, the gimlet tip may be produced for the screw after the manner seen in my Patent No. 1,465,148. Of course, in each such instance the thread is not interrupted by a cross groove, and when the screw is case-hardened or otherwise hardened so that the hardness of the thread will be sufficient to enable it to endure through an operation of entering the harder metals, such as soft iron or soft steel, the screw may be inserted in such harder metal after the manner taught in my several patents above mentioned. However, where the screws are to be introduced into a solid block or mass of metal, the bore or opening made to accommodate the body of the screw must be of an appreciably greater diameter than the root diameter of the screw to givethe requisite clearance and avoid the torsional strain and resistance to rotative movement as the thread advances in the work material. Accordingly, when the said screws are inserted they effect a highly satisfactory and dependable anchorage capable of resisting vibration loosening, but the deeper that the thread of the screw is embedded in the surrounding metal work, the greater the resistance to rotation, and this can be extended to the point where either the screw can not be physically forced in or else it will twist in two under the torsional strain.

It is an object of the present invention to produce at minimum expense highly efllcient screws and like anchorage instruments having the capacity to enter the surrounding work to greater depths and at substantially less resistance than the screws of my patents above mentioned while at the same time preserving substantially the same amount of capacity to resist vibration loosening. To this end, the present invention provides dies for rolling and includes an art of producing instruments of anchorage having the capacity to remove a portion of the surrounding wall of work of the harder metals, and to then compress and flow a remaining portion thereofalong the path of the entering threads so that the instrument of anchorage may be caused to enter the work to a greater depth and at less resistance than the screws of myabove mentioned patents and still have enough compressed material surrounding the threads that a reactive force is set up in the metal work causing a clamping action against the faces of the thread and highly resisting vibration loosening of the engagement between the thread and the surrounding metal.

In Figures 7 to 9 inclusive are shown embodiments of fastener instruments such as are adapted to be produced from the blank seen in Figure 6 when rolled on the dies seen in Figures 1 to 3, the dies being shown on a scale of approximately two diameters of the dies used for rolling fasteners having a thickness of one-eighth of an inch by an overall length of five-eighths of an inch, which is one of the popular smaller sizes, and the screw seen in Figure 7 is shown on a scale somewhat enlarged over the scale of the showing of the dies. It should, however, be understood that the invention is in no-sense limited to any particular size of fastener. The downward limit, that is the limit in smallness of the size of fastener possible to be made by the present improved rolling process, has probably'never been reached nor has the upward limit of increased size, since the smallest of such screws yet produced by me has had an overall length of three thirty-seconds of an inch with the details practically microscopic in size while the larger sizes range from two and one-fourth inches in overall length by seven-sixteenth inch in overall diameter (that is including the full depth thread) upward with no as yet determined limit, and if there be a limit to the rolling die but for its combination with the present improved die. The die I has the usual face ribs 2 and the customary roughened portion 3 at its entering end. The die I is preferably the stationary die in an automatic rolled screw machine set-up, and the roughened portion 3 ls, of course, at the place where the die first engaged the blank to be rolled.

Cooperating with the die I is a die 4 that is formed of two sections, one having the conventional die ribs 5 at its face corresponding to ribs 2, and the other having the outstanding, toothlike projections 6. The two sections of which die 4 is formed may be separate plates held in cooperative relatio'n by clamps, or may be an integral structure with the respective face portions produced by the die-forming art taught in my above-identified cd-pending application. The distinctive feature of the die 4 is the presence of the teeth 8, as the die otherwise is of conventional form corresponding to and adapted to be co-ordinated with the die I and having the roughened portion I at its beginning end or end first engaging the fastener blank, which end cooperates with the beginning end or end having the roughened portion 3 of die I for aiding in the starting of a rolling operation.

As plainly seen In Figure 2, the teeth I5 at the beginning end outstand to a height equal only to the height of the ribs 5 of die 4, and each at its outer end is preferably ridged with a slight angle (as seen both in Figures 2 and 4) to provide a gripping edge in starting the rolling operation of the blank, and the said teeth gradually increase in height and gradually lose their angle with successive teeth until the outer extremity becomes rounded, as seen at 8. The teeth Ii reach their farthest outstanding height at approximately midway of the length of the die 4, and then remain at a constant outstanding height throughout the balance of the length of the die and also, maintain their curved, outer.

end shape. The angle of the outer end of the teeth 6 at the beginning end of die 4 is seen in Figure 2, and it will also be seen in Figure 2 that the plane of the base of the valleys between the ribs or ridges 5 is indicated by the broken line 9 in Figure 2 from which it will be seen that the teeth 6 spring from a portion of the die 4 outward of said plane 9, so that even those teeth 6 at the entering end portion are of greater length than the depth of the grooves between ribs or ridges 5. Here outward is used to mean in the direction away from the cooperating die in use.

In Figure 6, it will be seen that the several teeth 6 throughout the whole length of the die are set substantially transversely of the lines of the ribs or ridges 5 so as to intersect a thread produced by similar ridges of a cooperating die but extended beyond the lateral extent of ridges 5. This transverse arrangement of the teeth I5 is susceptible of a wide range of variation in exact angularity relative to the ribs 5, but one desirable angle is seen in Figure 3 wherein the ribs S are set at a slightly acute angle to the faces of the die 4, the purpose of which is to cause the groove or grooves formed in the blank, as hereinafter described, to be set at such an angle as to provide for a shearing cut in the action of the ends of the thread sections intercepted by such grooves.

Each of the teeth 6 which is full length preferably has its free edge portion, as seen in Figure 5, inclined inward downwardly, so that the lower end of each tooth at the face of the die 4 is longer, as seen at III, than the length of the upper end or end adjacent the ribs or ridges 5. This inclination provides and compensates for and agrees with the inclination incident to the taper of the entering end portion of the blank to be treated, so that the groove to be formed by the teeth 6 will possess constant depth throughout their length notwithstanding the taper of the stock in which they are formed.

In Figure 6 is seen the blank II having the tapering entering end I2, which blank is well adapted for being rolled by the action of the dies I and 4. Of course, the blank II is formed of such material as soft iron or soft steel, and blanks of this kind in the practicing of the present improved art of rolling are fed successively between the dies and rolled after the manner indicated in Figure 2. This rolling operation consists of the introduction of the blank between the beginning end of die I and the beginning end of the die'4 seen at the left of Figure 3. Die 4, as soon as the blank is properly located, begins to make its stroke lengthwise of and across the full length of the die I, so that the blank II being engaged by the roughened portions 3 and I will begin to revolve between the die-faces, and will thereby be caused to have the metal of the blank body flowed to new positions producing the threaded and grooved condition seen in Figures '7 and 8. The die 4 continues its stroke until it passes the discharge end of die I which is the end opposite the roughened portion 3, and thereupon the completely rolled fastener structure formed from the blank II drops by gravity and is subject to such further treatment as may be required additional to the formation of the shape produced by the action of the dies. It will be noted that as the blank begins to turn at the roughened portions 3 and I, the 'ridges 2 and 5 begin to form up the thread I3, as seen in Figure 7, leaving between the successive helices the spiral valley I4 representing the minimum dam eter or rootdiameter of the body of the fastener being formed from the blank II. The maximum depth of such valley is not usually reached until the blank has progressed some distance along the dies and the ribs are slightly tapered in depth for that purpose. Of course, the ribs 2 and 5 can be made to outstand for the full depth from the beginning, and then the' full depth valley I4 will be produced by the first complete rotation of the blank, and will be smoothed off with the successive action of the die ridges as the blank-is moved across the balanceof the die. While the thread is being thus formed, which is a well understood and long practiced operation, the teeth 5 will also be acting to form grooves I5 in the tapered portion I2 of the blank which is to be the entering or leading end portion of the finished threaded fastener. The angle of the ridge of each of the teeth 6 at the beginning end of the blank bites into the tapered portion I2 of blank ii and wedges its way in which causes a lateral flowing and compression of the material of the blank and at the same time the ribs 2 of die I act to form thread helices on the said tapering portion I2, so that thread sections encircle the body of the fastener at the places of the grooves I5 and are interrupted by such grooves. As the die I .is of the fiat die type, having no outstanding, inclined ribbed portion at its edge that engages the tapered portion I2, the thread helices I6 along such tapered portion will not be of full outstanding dimension, but will gradually taper to a vanishing point in the body of the fastener at the extreme entering end thereof, as seen in Figure 7, and also a groove I! will be developed along the median line of such thread helices-tapering conversely to the taper of the thread parts l6 to the vanishing point at the beginning of the full outstanding depth thread I3. In view of the incline and the greater outstanding height of the ribs 6 at the places l0, the material of the blank II is depressed substantially to the same extent throughout thatportion of the taper i2 engaged by the teeth, and the grooves l5 are, therefore, of the same depth throughout their length. The grooves are thus rolled into the fastener while it is being rolled to form its thread, and no extra operation or cutting or severing of the material of the blank is required. Tapering thread helices like IS without the groove II can be readily produced by having the lower edge portion of die 4, that acts on the tapered part I! of blank H, inclined toward the cooperating die to compensate for the taper of part I2 and having the ridges 2 of such inclined part of the lower edge of the die properly tapered. Thus, the forming of the groove I1 is entirely optional and a matter of preference. The action of the teeth 6 is a compressing and flowing action which gives the surfaces of the grooves IS a greater compactness than other parts of the fastener and avoids injury to the fibre of the metal of blank II, and prevents production of raw edges at the places of intersection of the thread helices, such as result when grooves are formed by cutting and removal of material of the blank. The cutting edges at the ends of thread sections l6 produced by the grooves are also improved over those of cut grooves. Each groove I5 is preferably inclined in the direction of rotation of the fastener or screw, so that the cutting edges produced will have a slightly shearing action, and this inclination is given by the angle of the teeth 6, as plainly seen in Figure 2, which, as above described, is a slightly acute angle to the faces of the die I. The inclination is preferably such that the major axis of each groove I5 is parallel to a line drawn tangent to the taper of the finished thread at the entering end of the fastener as seen in elevation; but, of course, the grooves maybe set at any other desired angle, whether directly upright or otherwise, according to the extent of shearing action desired or the omission of it,

While there is shown in Figures '7 and 8 a finished structure having three grooves IS, the number of grooves may be varied as desired and will be controlled by the spacing of the teeth '6 with respect to the diameter of the blank to be rolled between the dies. By slightly decreasing the spacing of the teeth, as seen in Figure 3, four grooves l5 may be produced on a screw of the same diameter as shown in Figure 9, the parts in Figure 9 being otherwise identical with the parts seen in Figures 7 and 8. Of course the head ill of the fastener seen in Figures '1 and 8 may be of any desired shape and formed with any preferred tool-receiving well, pocket or groove, or otherwise shaped to receive a rotating tool for turning the fastener into place.

It will be understood, of course, that the blank II is in its soft condition when rolled, and is still soft when the rolling operation is completed, there being no appreciable hardening in the mere increased compactness resulting from the rolling operation. It will also be understood by reference to my above-mentioned patents that after the rolling operation the screw orlike fastening instrument is case-hardened or otherwise hardened in the sense of having its malleability largely or practically wholly destroyed, as by carbon impregnation and chilling. One very satisfactory and acceptable mode of hardening is by cyanide treatment where the operation consists preferably of preheating the fastener instrument, dropping it into molten cyanide at high temperature, say 1600 F., or thereabout, and, after exposure sufficient for the required carbon impregnation from the cyanide, withdrawing from the cyanide and quenching at the high temperature. This, of course, is only one of various modes that are entirely acceptable for providing the requisite hardness for the intended use, which hardness should be sufficient to enable the thread to enter the harder metals, such as soft iron or soft steel, substantially without injury to the thread, and preferably the hardness should be sufficient to enable the thread to enter without injury to the harder metals, such as steel having a high carbon and manganese content and semi-annealed. The hardness, however, should not be extended to the point of brittleness. Toughness and stability must be preserved while providing the desired hardness.

It, of course, is well understood that when screws are being rolled, the heads outstand above the upper surface of the rolling dies, and the rolling operation will occur on the blank throughout those portions of the blank in engagement with the dies, and it follows, therefore, that the fastener made in accordance with the present invention and with the use of the present improved die may have grooves l5 of greater or less length according to the length of the blank and the extent to which it extends across the tooth portion of the die 4, that is the portion having the teeth 6. Also, it should be understood that while the illustrative embodiments seen in Figures 6 to 9 inclusive are substantially enlarged with respect to the popularly commercial product of the smaller types of screws, it is easily possible to produce fastener instruments of the size shown in the drawing and much larger. Also, the enlargement of the showing of these fasteners in the drawing is not with any exact reference or proportion rel ative to the dies seen in Figures 1 to 5 inclusive. The said dies themselves may be considered enlarged showings of dies for a popular size of rolled thread fastener, and the fasteners shown in the drawing merely illustrate the results obtained. The scale of the showing is used to facilitate disclosure of detail, but without restriction to any necessarily fixed size or proportion of parts relative to the proportion of parts of the dies.

The anchorage instrument produced by the present improved art is thus referred to in generic terms,though usually it will assume the form of screws for regular use in metal work, and might well be mentioned as screw-threaded fasteners; but the thus produced anchorage instruments are capable and well adapted to be inserted into.

work to form a thread path and then backed off or rotated out by reverse rotation to leave a thread path for the introduction of a screw having the same thread characteristics without necessarily possessing the same thread form of entering end. Thus, the anchorage instrument produced by the present invention is susceptible of use as a substitute for a tap, but is also well adapted for and capable of and chiefly used as an anchoring screw.

It is well understood by those who have made scientific, and particularly microscopic, studies of milled, sawed, filed, or cut or similarly severed or abraded metal that the edge or surface left after such severance is comparable to the raw edge of a piece of woven fabric which has been cut, as by the use of a pair of scissors, and has not been provided with a selvage or a hem. On the other hand, metal, and particularly malleable iron and steel, when cold flowed or manipulated as a succession of kneading operations achieves a surface along the area thus treated which is comparable to a selvage edge in a piece of woven fabric, so that the surface portions of the thus kneaded or similarly manipulated or flowed metal possesses stability and durability greater than that of the raw surface left from the shearing action of a;

stantial part of the work of providing entry for the fastener, in the best possible condition to endure throughout the entering operation and to remain substantially uninjured by such operation. Thus, the physical form and condition of the entering end of the fastener become important, and added to this importance is the further value arising from the fact that the grooves l5 terminate within the length of the tapered entering end portion of the fastener and do not extend to the full depth thread l3. Accordingly, when the edges formed by grooves l5 remove metal from the surrounding work to begin the formation of a thread path to receive the thread l3, the tapering portion of the thread beyond the grooves I5 is compelled to enlarge the thus partially formed path, and such enlargement is graduated uniformly inversely proportionate to the taper of the thread until the thread reaches full depth, at which point the thread path or internal thread being formed by the screw becomes of a dimension sufficient to accommodate the successive advancing helices of the full depth thread l3. In so doing, however, the fact that the metal of the work entered is being kneaded or manipulated by the tapering portion of the thread up to the full depth thread beyond the grooves l5 produces the two very desirable results, first, of finishing the surface of the engaged work throughout the Walls of the internal thread or path for the thread, that is, the "raw condition of the surfaces caused by the cutting action of the thread-ends provided by grooves is are eliminated and given the compactness incident to cold flowing; and second, of setting up and creating a reactive force in the body of the surrounding work in its tendency to resist the greater compactness caused by the action of the entering tapered thread, which force efiects a gripping action or frictional engagement of the surrounding work with the several thread helices it, and leaves no thread clearance or freedom for ease of insertion and removal as is invariably present where an internal thread is tapped and thus previously prepared for the insertion of a machine screw. Thus, the resulting anchorage of the screw in metal work is particularly efiective in resisting vibration loosening or withdrawal stresses. In other words, substantially the advantages,-so far as effective anchorage is concerned, that are obtained by the screw of my Patent No. 1,809,758, above referred to are secured by the present improved screw with the further advantage of greater ease of introduction to a greater depth in the work without prohibitive resistance to the required torsional stress on the screw while it is being rotated into the work. Yet, of course, the fastener is entirely capable of being screwed out and another screw inserted to a tight fit.

It should also beapparent that so far as the art of forming grooves in screws is concerned, while the preferred steps involve the kneading of the metal of the screw blank to the grooved condition through the use of projections on a die, such as teeth 6, it is obviously possible to practice the art by quite a wide range of other apparatus than the die structure shown. For example, appropriately located and coordinated reciprocating punches may be mounted to act uponthe tapering stock l2 of blank It at an appropriate intermediate point in the rolling of the thread, or it is even possible to stamp grooves similar to grooves IS in the portion l2 of blank H in a stamping machine preceding completion of the rolling operation for forming the threads, except for the objection of the thus required additional operation; whereas by the rolling of the threads l3 and i6 and grooves [5 at one and the same time or the rolling of the thread and the punching of the grooves at one and the same time, the product is secured, so far as thread and grooved formation is concerned, by a singleoperation.

While it will be seen fromthe foregoing that the grooves I5 are preferably limited in their length, it is entirely feasible, according to the present invention, to extend the length of the grooves as much as may be desired by a mere increase in the corresponding dimension of the teeth 6. Furthermore, it should be noted'that when the blank ll reaches the point approximately indicated by the reference numeral 8 in Figure 2, the thread rolling and groove forming action on the blank will have been completed in the sense of there having been created the full depth thread IS, the tapered thread portion it with its groove i1, and the grooves I5; 'but since the grooves l5 intersect the thread iii the likelihood of burrs or extruded material appearing along the groove and about the ends of the sections of the thread portion Hi, the further rolling of the screw is desirable to the end of the respective dies, that is until the righthand end of die 4, as seen in Figure 2, passes beyond the lefthand end of die I, as seen in Figure 2. This further rolling repeatedly cleans and redistributes extruded metal and kneads and manipulates the same until, when the screw is finally dropped by the fact that the die t passes beyond die l, the thread valleys, thread ends,and grooves (it) will all be entirely clear and thoroughly cleaned and Worked to the finished condition free of burrs or projections. Furthermore, the fibre of the material is left largely unbroken and long fiber thereof extends about the several grooves uninterrupted as they would be if the grooves were out instead of being rolled into the blank.

intended The present improved art and apparatus are especially well adapted to produce fastener in struments as disclosed in my co-pending application filed even date herewith, the disclosure of which is incorporated herein by reference, and which fasteners correspond substantially to those seen in the instant drawing in Figures 7, 8, and 9.

What is claimed is:

1. In the art of forming screw-threaded fastener instruments, rolling a blank between dies and thereby simultaneously forming thereon a thread with a tapering portion and a series of cirthe thread only in said tapering portion and extending into the body of the blank inward of the thread.

2. In the art of forming screw-threaded fastener instruments, treating a blank for forming a thread thereon and a groove therein intersecting the thread and extending into the body of the finished instrument, the formation of the thread and groove being effected in a single operation.

3. A die for rolling a screw thread on a blank and a groove intersecting the thread thereof comprising a die block having thread-forming ridges on its face throughout a portion of the width of the die and projections outstanding at another portion of said face in position to form said groove in the course of the rolling of a thread on a blank incident to the engagement of the blank with said die face, the groove-forming projections being arranged throughout the length of that edge portion of the face of the die corresponding to the entering end portion of the finished screw and tapered to compensate for a taper of the blank.

4. A die for rolling a thread on a blank and a groove intersecting the thread thereof comprising a die block having thread-forming ridges on its face and projections graduated in height and outstanding at said face in position to form said groove in the course of the rolling of a thread on a blank.

5. A die as claimed in claim 4 with additional non-graduated projections at the face thereof.

6. A die for rolling a screw thread on a blank and a groove intersecting the thread thereof comprising a die block having thread-forming ridges on its face throughout a portion of the width of the die and projections outstanding at another portion of said face in position to form said groove in the course of the rolling of a thread on a blank incident to the engagement of the blank with said die face, the grooveforming projections being arranged throughout the length of that edge portion of the face of the die corresponding to the entering end portion of the finished screw and terminating in ridges having each an angle providing a gripping edge located to engage the blank.

'7. A die for rolling a screw thread on a blank and a groove intersecting the thread thereof comprising a die block having thread-formingridges on its face throughout a portion of the width of the die and projections outstanding at another cumferentiaily spaced grooves therein intersecting portion of said face in position to form said groove in the course of the rolling of a thread on a blank incident to the engagement of the blank with said die face, the groove-forming projections being arranged throughout the length of that edge portion of the face of the die corresponding to the entering end portion of the finished screw, some of the projections at the beginning end portion of the die terminating in ridges having each an angle providing a gripping edge located to engage a blank to aid in rolling the blank as well as begin formation of a groove therein, and other of the projections being rounded at their terminals to finish the groove.

8. A die for rolling a screw thread on a blank and a groove intersecting the thread thereof comprising a die block having thread-forming ridges on its face throughout a portion of the width of the die and projections outstanding at another portion of said face in position to form said groove in the course of the rolling of a thread on a blank incident to the engagement of the blank with said die face, the groove-forming projections being arranged throughout the length of that edge portion of the face of the die corresponding to the entering end portion of the finished screw, the projections having inclined exposed end portions to compensate for a taper of the blank.

9. The method of rolling a turn screw with a spiral thread interrupted by grooves, which comprises rolling the thread valleys and the grooves progressively deeper throughout the early portion of the rolling operation, and continuing the thread and groove pressing operations to uniform full depths throughout the latter portion of the rolling operation.

10. A thread rolling die for use in rolling a turn screw with a spiral thread interrupted by longitudinal grooves, said die having throughout a portion of its width a series of thread rolling ribs, and having in another portion of its width a series of groove forming projections, there being a plu-- rality of such projections uniformly spaced in each full turn length of the die, the groove forming projections at the introductory end of the die being of progressively increasing height, and the groove forming projections being of substantially uniform height through a trailing end portion of the die corresponding at least to a plurality of screw turns.

HEYMAN ROSENBERG. 

